In both of the above-identified, patents of Albert R. Uhlig, there is disclosed a blow molding method and apparatus wherein a tubular parison is blown to a blown pre-form, and this pre-form is then blown to the final article. This two-step blowing process is quite advantageous in that it (1) substantially doubles the output capacity of the blow molding machine, (2) cools the blown pre-form so that the final blowing operation can be carried out while the blown pre-form is at a temperature conducive to bi-axial orientation, and (3) makes possible the blowing of articles such as handled containers with minimal flash.
Generally, these prior processes include the provision of separate and distinct blowing molds for the pre-form and for the final article, and these molds are jointly displaced relative to the fixed parison forming station. The entire mass of both the pre-form blow mold and the final blow mold, together with their related clamping equipment, must be transported toward and away from the parison forming station.
This necessity for transporting the entire mold weight, including the large final blow molds has imposed some severe restrictions on the size of machines of this type. For example, the manufacture of large containers and the utilization of multiple cavities for the simultaneous manufacture of several containers has been inhibited because of the large mass of molds and clamping equipment which must be transported. Further, the necessary tie bars and the size of the mold-carrying platens has also limited the design to a relatively small mold clamping area.